Recovery of fluid such as gas and or oil from a subterranean formation is frequently troublesome when the subterranean formation is composed of one or more incompetent sand layers or zones. Sand particles in the incompetent or unconsolidated sand zone migrate into the well bore during recovery of formation fluids from the zone or zones immediately adjacent to the unconsolidated sand-containing zones. Similar problems are encountered when injecting fluids into formations during the course of secondary or tertiary recovery operations being applied to subterranean formations. The most troublesome problem is encountered while recovering fluids from the formation, in which instance the movement of sand particles into the well bore cause the well to "sand up" and as a consequence thereof, further production of fluids from the well is made difficult or impossible. Small sand particles can also plug small openings in porous masses formed around the well bore for the purpose of restraining the flow or particulate matter such as sand or gravel into the well, resulting in terminating further production of fluid from that particular well. Another adverse results of sand particle migration into the producing well is the rapid wear of the tubular goods or mechanical equipment when the abrasive sand particles are transported to the surface along with the fluids being produced, and brought into contact with pipes, pumps, and other surface equipment being used to recover and transport formation fluids.
Many methods are described in the prior art for preventing or decreasing the flow of undesirable particulate matter such as sand during the course of recovering formation fluids from production wells. These include the placement of mechanical screens, filters, perforated or slotted lines, etc., around the production tubing present in the well bore. While these devices have been of limited success in some instances, they are not always entirely satisfactory for a number of reasons. The mechanical devices restrain only the larger sand particles and are not completely effective for restraining the flow of very fine sand particles from the formation into the well and then to the surface of the earth. Many of these devices interfer with completion and work over operations.
Chemical compositions for forming permeable barriers around the well bore have been described in the literature and used in the field with success in some instances. Resinous plastic materials are injected into a mass of unconsolidated sand, either naturally occurring formation sand or sand which has been placed in a cavity created adjacent to the well bore for that purpose, the resinous plastic material bonding the sand particles together. Numerous difficulties are encountered during commercial applications of this technique, but even when the permeable mass can be formed satisfactorily, it is not effective and satisfactory for use in producing wells producing viscous petroleum, the production of which is being stimulated by thermal recovery means such as by injection of steam into the formation. The consolidated sand masses are rapidly degraded by passage of high temperature, sometimes alkaline steam through the sand restraining barriers.
In view of the foregoing discussion, it can be appreciated that there is a substantial, unfulfilled need for a sand control method capable of preventing the flow of unconsolidated mineral particles including sand into or away from the well bore during a period of fluid injection. More particularly, there is a need for an inexpensive, reliable method of controlling the flow of sand into or away from the well in a formation which is sufficiently resistant to hot, alkaline fluids to permit its use in formations being stimulated by injection of high temperature alkaline fluids such as steam and caustic.
By the method of the present invention one is able to treat underground formations so as to accomplish consolidation of granular materials such as sand or gravel into a permeable, competent and consolidated mass, which effectively restrains the movement of unconsolidated sand particles into or away from the well bore, which consolidated permeable mass will not be appreciably affected by subsequent contact with hot alkaline fluid such as steam or a mixture of steam and an alkalinity agent such as caustic, thus avoiding many of the disadvantages of prior art methods, both mechanical and chemical.